Differences:
1. structure- Each granum consists of 5-25 disc shaped thylakoids stacked one on the other resembling a stack of coins. Stroma is a fluid filled matrix containing DNA , ribosomes , enzymes, oil droplets and starch grains.
2 .location - grana are found in the stroma while stroma is found within the inner membrane of the chloroplast.
3. enzymes - grana contain enzymes needed for light dependent reactions while stroma contains enzymes used in light independent reactions of photosynthesis
4. function - grana provide a large surface area for the attachment of chlorophylls while stroma houses the sub-organelles of chloroplasts.
Similarities.
1.Both grana and stroma are found within the chloroplast
2. Both grana and stroma take part in the process of photosynthesis.